Today isn't Patch Tuesday - or any kind of Tuesday - but Microsoft has released a new cumulative update for PCs running version 1607, otherwise known as the Anniversary Update. The build replaces 14393.953, which was released last Tuesday.
KB4015438 is a minor update, only listing two fixes:
Addressed a known issue with KB4013429 that caused Windows DVD Player (and 3rd party apps that use Microsoft MPEG-2 handling libraries) to crash.
Addressed a known issue with KB4013429, that some customers using Windows Server 2016 and Windows 10 1607 Client with Switch Embedded Teaming (SET) enabled might experience a deadlock or when changing the physical adapter’s link speed property. This issue is most commonly seen as a DPC_WATCHDOG_VIOLATION or when verifier is enabled a VRF_STACKPTR_ERROR is seen in the Memory dump.
The Windows DVD Player app isn't one that's pre-installed on your PC; in fact, it costs $14.99 in the Windows Store. It's clearly an issue with Windows though, rather than the app itself, as it affects other applications that have similar functionality.
Today's cumulative update is available for PCs only, so Windows 10 Mobile users are once again left out. This is bad news for the platform, as it's been waiting to get patched for a security vulnerability that leaves your photos exposed while the phone is locked for over a month now.
Nevertheless, Windows 10 for PCs build 14393.969 is available in the Production and Release Preview rings right now, and you can get it by heading over to Settings -> Update & security -> Windows Update -> Check for updates.